⚙️ [Maintenance]: Markdown pages can carry both a front matter title and a body heading (#39)

Markdown pages in repositories generated from this template can now
carry both a front matter `title:` and a body `# Heading` without the
linter objecting. MkDocs keeps using the front matter title for
navigation and the page title, and the body heading keeps rendering on
github.com, where front matter is shown as a table rather than a title.

## Fixed: A front matter title is no longer counted as a second
top-level heading

The markdown linter shipped with the template applied markdownlint's
default `front_matter_title` pattern, so a front matter `title:` was
treated as the document's top-level heading. Any page that also opened
with `# Heading` was reported as `MD025/single-title/single-h1 Multiple
top-level headings in the same document`, and the author was pushed
toward dropping one of the two — losing either correct site navigation
or a readable page on GitHub.

Nothing needs to change in your repository. Repositories generated from
the template inherit the fix, and existing repositories pick it up the
next time they take the template's linter configuration.

MD025 still does its job: a page with two body `# Heading` lines is
reported exactly as before.

---
<details>
<summary>Technical details</summary>

`.github/linters/.markdown-lint.yml` gains one block in the "Rules by
id" section, in numeric order between `MD024` and `MD026`:

```yaml
MD025:
  front_matter_title: '' # Allow a body H1 alongside the front matter title
```

- **Empty pattern rather than `MD025: false`.** `frontMatterHasTitle()`
in markdownlint treats a defined-but-falsy pattern as "ignore front
matter" while leaving the rest of the rule active, so a genuinely
duplicated body `# Heading` is still reported. Disabling the rule
outright would stop catching that too, which is a real defect rather
than a formatting preference.
- **Converges with MSXOrg/docs**, which carries `front_matter_title: ""`
with the same comment in its copy of this file. Single quotes are used
here to match the one existing quoted value in this file (`punctuation:
'.,;:!。，；:'`); `''` and `""` are the same empty YAML scalar, and
markdownlint sees an identical value either way.
- **No other rule was touched.** The wider drift from MSXOrg/docs —
`MD013` line length (808 vs 3000), `MD041`, `MD051`, `MD060` — is
visible but deliberately out of scope.
- `PSModule/Markdown` carries a byte-identical copy of this file and hit
this exact problem in PSModule/Markdown#33, where `title:` had to be
stripped from three documentation files to get a green lint run. Fixing
the template is what stops that repeating in every module repository.

**Verification.** Throwaway fixtures outside the repository, ephemeral
`npx`, nothing added to the repo. Run against both
`markdownlint-cli@0.45.0` (the CLI super-linter drives) and
`markdownlint-cli2@0.23.2` (markdownlint v0.41.1); the two agree on
every case.

| Case | Config | Result |
| --- | --- | --- |
| Front matter `title:` + body `# Heading` | before | `MD025` reported
at the body heading — reproduces the bug |
| Front matter `title:` + body `# Heading` | after | Clean, exit 0 |
| Two body `# Heading` lines | after | `MD025` still reported at the
second heading |
| The repository's own 8 Markdown files | after | Clean, exit 0 |

Implementation plan progress: both plan sections in
#38 — configuration and verification — are
complete. Nothing deferred.

| Changed surface | Standards checked | Framework docs checked | Result
|
| --- | --- | --- | --- |
| `.github/linters/**` (linter configuration) | MSXOrg Coding Standards
| Repository Defaults | Aligned |

Issue convergence sweep: the scope was every open issue in
`PSModule/Template-PSModule`. #38 is the only one, and it is the closing
issue for this pull request.

</details>

<details>
<summary>Relevant issues (or links)</summary>

- Fixes #38

</details>

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: MariusStorhaug

.github/linters/.markdown-lint.yml

@@ -14,6 +14,8 @@ MD007:
 MD013:
   line_length: 808 # Line length
 MD024: false # no-duplicate-heading, INPUTS and OUTPUTS _can_ be the same item
+MD025:
+  front_matter_title: '' # Allow a body H1 alongside the front matter title
 MD026:
   punctuation: '.,;:!。，；:' # List of not allowed
 MD029: false # Ordered list item prefix